1. Field of the Invention
The present invention relates to a process for producing 1,1-diaryl alkanes by condensation of aromatic compounds with acetals using a perfluorinated sulfonic acid in polymeric form as catalyst.
2. Description of the Background
Methods of producing diaryl alkanes are known in the art.
JP 02-134332 A discloses a process for producing diaryl methanes which comprises reacting aromatic hydrocarbons and formaldehyde in the presence of a sulfuric acid catalyst and in the presence of surfactants.
FR 2745285 A1 discloses the C-alkylation of aromatic compounds using a particular catalyst, which catalyst comprises a rare earth on a clay, silica and/or alumina support.
U.S. Pat. No. 4,814,537 A discloses a process for preparing methyl-substituted diphenyl methanes by coupling methyl-substituted benzene by contacting with a solid heterogeneous catalytic oxide of vanadium, molybdenum, rhenium and/or tungsten.
U.S. Pat. No. 4,895,988 A discloses the condensation of aromatic compounds with carbonyl compounds, such as phenol(s) with formaldehyde, catalyzed by specific zeolite(s), to produce diaryl alkanes.
US 2003/0013932 A1 discloses a process for producing diaryl methanes and their derivatives, using a methylenating agent such as formaldehyde in the presence of a heteropoly-acid catalyst.
Tetrahedron Letters (2006) 47 (14), 2291-2294 discloses the synthesis of diaryl methanes via InCl3-4H2O-catalyzed dehydration of electron-rich arenes with trioxane.
U.S. Pat. No. 6,207,866 discloses a process for producing diaryl methane or its derivatives by reacting dimethoxymethane (DMM) and an aromatic compound at a reaction temperature in the range of 80 to 400° C. in the presence of an acid catalyst. The patent discloses further that the DMM may be prepared by the reaction of an alcohol and formaldehyde in the presence of an acid catalyst.
The issue with the above mentioned prior art is that the reported isomer selectivity when the reaction involves substituted aromatic compounds such as xylene, is poor. In addition, the reaction yields are not acceptable. Above-referenced U.S. Pat. No. 6,207,866 lists acidic cation exchange resins such as sulfonated styrene-divinyl benzene copolymer and sulfonated perfluoroethylene copolymer under the trade name Nafion® in the preparation of above-discussed DMM from an alcohol and formaldehyde.